Process for the production of molten pig iron or steel pre-products and a plant for carrying out the process

ABSTRACT

In a process for the production of molten pig iron (12) or steel pre-products from fine particulate iron-containing material, in particular reduced sponge iron, in a meltdown gasifying zone (6) of a melter gasifier (5) the iron-containing material is melted in a bed (16) formed of solid carbon carriers, under the supply of carbon-containing material and oxygen-containing gas at the simultaneous formation of a reducing gas. To prevent the fine particles of the iron-containing material charged to the melter gasifier from being discharged, the iron-containing material is supplied into the a melter gasifier (5) centrally, closely above the bed (16) but in its immediate vicinity, by means of an oxygen-burner (15) under the formation of a high-temperature combustion zone (21).

BACKGROUND OF THE INVENTION

The invention relates to a process for the production of molten pig ironor steel pre-products from fine-particulate iron-containing material, inparticular reduced sponge iron, in a meltdown gasifying zone of a meltergasifier, in which, under the supply of carbon-containing material andoxygen-containing gas at the simultaneous formation of a reducing gas,the iron-containing material is melted in a bed formed of solid carboncarriers, optionally upon previous complete reduction, and a plant forcarrying out the process.

EP-B-0 010 627 teaches a process for the production of molten pig ironor steel pre-products from particulate iron-containing material,particularly prereduced sponge iron, and for the production of reducinggas in a melter gasifier, wherein by the addition of coal and by blowingin an oxygen-containing gas a fluidized bed is formed of coke particles.Here, the oxygen-containing gas or pure oxygen respectively are injectedinto the lower region of the melter gasifier. The particulateiron-containing material, particularly prereduced sponge iron, and thelumpy coal are fed in from above, through charging openings arranged inthe hood of the melter gasifier, the descending particles are sloweddown in the fluidized bed and the iron-containing particles are reducedand melted while falling through the coke fluidized bed. The molten andslag-covered metal collects at the bottom of the melter gasifier. Metaland slag are drawn off through separate tap openings.

A process of this kind is, however, not suited for processingfine-particle sponge iron, as fine-particle sponge iron would bedischarged from melter gasifier at once, due to the pronounced gas flowexisting within the same. Discharging is further promoted by thetemperature reigning in the upper region of the melter gasifier, sinceit is too low to ensure melting of the sponge iron at the charging site.

From U.S. Pat. No. 5,082,251 it is known to directly reduceiron-containing fine ore in a fluidized bed operation by means of areducing gas produced from natural gas. In this process the fine ore,which is rich in iron, is reduced by means of a reducing gas, atelevated pressure, in a system of fluidized bed reactors arranged inseries. The sponge iron powder thus obtained is subsequently subjectedto hot or cold briquetting. For further processing the sponge ironpowder, separate melting facilities have to be provided.

From EP-A-0 217 331 it is known to directly prereduce fine ore in afluidized bed process and to feed the prereduced fine ore to a meltergasifier and to completely reduce it by means of a plasma burner underthe supply of a carbon-containing reducing agent and to melt it. In themelter gasifier, a fluidized bed forms and thereabove a fluidized bed ofcoke. The prereduced fine ore or the sponge iron powder respectively aresupplied to a plasma burner provided in a lower section of the meltergasifier. One disadvantage here is that by feeding the prereduced fineore immediately in the lower melting region, i.e. in the region wherethe melt collects, complete reduction is no longer ensured and thechemical composition required for further processing of the pig ironcannot be achieved in any event. Moreover, charging of substantialamounts of prereduced fine ore is not feasible, due to the fluidized bedor fixed bed respectively forming from coal in the lower region of themelter gasifier, as it is not feasible to discharge a sufficient portionof the melting products from the high-temperature zone of the plasmaburner. Charging of more substantial amounts of prereduced fine orewould instantly lead to thermal and mechanical failure of the plasmaburmer.

From EP-B-0 111 176 it is known to produce sponge iron particles andmolten pig iron from lumpy iron ore, the iron ore being directly reducedin a direct-reduction aggregate and sponge iron particles dischargedfrom the direct-reduction aggregate being separated into a coarse andfine-grain fraction. The fine-grain fraction is supplied to a meltergasifier, in which the heat required for melting the sponge iron as wellas the reducing gas supplied to the direct-reduction aggregate areproduced from charged coal and supplied oxygen-containing gas. Thefine-grain fraction is conducted into the melter gasifier via a downpipeprojecting from the head of the melter gasifier as far as into thevicinity of the fluidized bed of coal. At the end of the downpipe abaffle plate is provided in order to minimize the velocity of thefine-grain fraction, and consequently the exit velocity of thefine-grain fraction on leaving the downpipe is very low. At the chargingsite, the temperature reigning inside the melter gasifier is very low,as a result of which immediate melting of the supplied fine-grainfraction cannot take place. This and the low exit velocity from thedownpipe lead to a substantial portion of the supplied fine-grainfraction exiting from the melter gasifier along with the reducing gasproduced in the same. In accordance with this process it is not possibleto charge a more substantial amount of fine grain or to charge finegrain exclusively.

In a process according to EP-A-0 576 414 lumpy iron-ore-containingcharging substances are directly reduced in a reduction shaft furnace,by means of the reducing gas formed in the meltdown gasifying zone. Thesponge iron thus obtained is subsequently fed to the meltdown gasifyingzone. In order to be able to additionally utilize fine ore and/or oredust, such as oxidic iron fine dust incurring in a metallurgical plant,with this known process, the fine ore and/or the ore dust along withsolid carbon carriers are supplied to a dust burner working into themeltdown gasifying zone and are reacted in a substoichiometriccombustion reaction. A process of this kind enables efficient processingof fine ore and/or ore dust incurring in a metallurgical plant, and thatup to an order of magnitude of 20 to 30% of the total ore charge, andthus enables a combined processing of lumpy ore and fine ore.

SUMMARY OF THE INVENTION

The invention aims at avoiding these drawbacks and difficulties and hasas its object to provide a process of the initially described kind and aplant for carrying out the process enabling the processing offine-particulate iron-containing material, without any need forbriquetting, and wherein on the one hand any discharge of the suppliedfine particles, i.e. of the iron-containing material, optionally in theprereduced or in the completely reduced state, by means of the reducinggas produced in the melter gasifier is reliably avoided and wherein onthe other hand a possibly required complete reduction is ensured. Oneparticular object of the invention is to create a process enabling theprocessing of a charge the majority of which, preferably 100%, are madeup of fine-particulate iron-containing material to obtain pig ironand/or steel preproducts, while utilizing a melter gasifier.

According to the invention this object is achieved in that theiron-containing material is supplied into the a melter gasifiercentrally, closely above the bed but in its immediate vicinity, by meansof an oxygen-burner under the formation of a high-temperature combustionzone, wherein preferably a burning jet formed in the high-temperaturecombustion zone is directed towards the surface of the bed and isutilized for blowing the iron-containing material towards the surface ofthe bed.

On the surface of the bed the velocity of the fine-particulateiron-containing material is slowed down, so that a retention time isachieved in the high-temperature zone that is sufficient for melting thesupplied iron-containing material. Slag and iron can run off through thefluidized or fixed bed respectively toward the lower section of themelter gasifier. Due to the retention time ensured in the meltdowngasifying zone complete reduction of any iron-containing material notyet completely reduced at this stage is ensured.

From EP-A-0 174 291 it is known to supply dustlike sulfidic nonferrousmetal ores, particularly nonferrous metal ores, to a melter gasifier viaa melter-burner. Even more substantial amounts of sulfidic nonferrousmetal ores can be processed here, as the heat required for melting theore particles is produced by exothermic reaction of the sulfidic orewith oxygen in the burner.

With this known process, the coal for forming a fluidized bed of carbonis charged into the meltdown gasifying zone separately. With a processof this kind it is not feasible to oxidic fine ores, as the heat thatwould cause these oxidic fine ores to melt would not be available here.As a result, due to the fine ore supply duct being arranged at the upperend of the melter gasifier, these fine ores would be discharged by thereducing gas which emerges from the meltdown gasifying zone and isdischarged from the melter gasifier.

To prevent the fine-particulate iron-containing material charged intothe meltdown gasifying zone from being oxidized by the oxygen oroxygen-containing gas supplied to the oxygen burner, according to theinvention advantageously fine coal is introduced, or preferably blowninto the high-temperature combustion zone directly.

According to a preferred embodiment fine ore is reduced in the fluidizedbed process by means of the reducing gas formed in the meltdowngasifying zone, wherein the reducing gas emerging from the meltergasifier is conveyed to the fluidized bed reduction directly, i.e.without prior dust separation. In the process, the coke dust dischargedfrom the meltdown gasifying zone along with the reducing gas is fed tothe fluidized bed reduction zone and thereby reduces the danger of"sticking". Along with the reduced fine ore it is subsequently fed tothe meltdown gasifying zone again, via the oxygen burner, so that itwill not be lost.

Advantageously lumpy carbon-containing material as well as lumpyiron-containing material, which, in view of their size, cannot bedischarged along with the gas stream, are additionally introduced intothe meltdown gasifying zone via supply ducts leading into the uppersection of the melter gasifier. Thus with the process according to theinvention conventional melter gasifiers may be employed without anymajor constructional changes.

A plant for carrying out the process, comprising a melter gasifierincluding supply and discharge ducts for adding carbon-containingmaterial, iron-containing material, for discharging the reducing gasproduced and for feeding oxygen-containing gas, as well as a slag andiron-melt tap, wherein a lower section of the melter gasifier isprovided for collecting the molten pig iron and the liquid slag, asuperimposed central section is provided for accommodating a bed ofsolid carbon carriers and subsequently an upper section is provided as akilling space, characterized in that a burner supplying anoxygen-containing gas and fine-particulate iron-containing material intothe melter gasifier is provided whose burner head is arranged at thetransition from the central section to the upper section in the heart ofthe cross section of the killing space, wherein suitably the burner headis directed towards the surface of the bed.

Preferably, lance openings of supply lances feeding fine coal areprovided in the immediate vicinity of the burner head.

In accordance with a preferred embodiment the burner is designed as aburning lance protruding into the interior of the melter gasifiervertically and centrally, departing from the head of the meltergasifier. The burner may for example be constructed as described inEP-A-0 481 955. In addition it may be provided with an annular gap forsimultaneously supplying solid fine-particle coal.

Suitably the supply lances protrude into the melter gasifier departingfrom the side, preferably slanting downward.

It is of advantage if, departing from the killing space of the meltergasifier, a reducing-gas discharge duct runs directly, i.e. with no dustseparating means arranged intermediately, into a fluidized bed reactorutilized for directly reducing fine-particulate iron ore, and thatdeparting from the fluidized bed reactor a duct for discharging reducedfine ore runs into the burner.

BRIEF DESCRIPTION OF THE DRAWING

The sole drawing FIGURE schematically illustrates an examplaryembodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The plant according to the invention is provided with a fluidized bedreactor 1, into which iron-containing fine ore or iron-containing ore(f.i. 1461 kg ore/ton pig iron) containing a considerable portion (morethan 50%) of fine ore is fed through an ore feed duct 2. In thisfluidized bed reactor 1 a pre- or optionally a complete reduction of thefine ore is carried out in a fluidized bed zone 3.

Details concerning the ore:

Fe_(tot) 66.3%

Fe₂ O₃ 94.7%

grain size 0 to 8 mm

Instead of the single fluidized bed reactor 1 it is feasible to provideseveral fluidized bed reactors consecutively arranged in series, whereinthe fine ore is conducted from fluidized bed reactor to fluidized bedreactor via conveying ducts, similar to the manner described in US-A-05,082,251.

The pre- or completely reduced fine ore, that is to say the sponge ironpowder (530 kg/ton pig iron), is supplied to a melter gasifier 5 througha conveying duct 4, in a manner that will be described in more detailbelow. In the melter gasifier 5, in a meltdown gasifying zone 6, a CO-and H₂ -containing reducing gas (1715 Nm³ /ton pig iron at 850° C.) isproduced from coal and oxygen-containing gas and is fed to the fluidizedbed reactor 1 via a reducing-gas feed duct 7.

Analysis of the reducing gas:

Co 63.4%

Co₂ 4.3%

H₂ 26.3%

balance (H₂ O, N₂, CH₄)

The reducing gas then streams through the fluidized bed reactor 1 incounterflow to the ore flow and is discharged from the fluidized bedreactor 1 via a top-gas discharge duct 8 and subsequently is cooled andscrubbed in a wet scrubber 9 and then is made available to consumers asa top gas (1639 Nm³ /ton pig iron).

Analysis of the top gas:

Co 42%

C0₂ 33.2%

H₂ 18.4%

balance (H₂ O, N₂, CH₄)

calorific value of the top gas: 7681 kJ/m³ normal

The melter gasifier 5 is provided with supply ducts 10 for solid carboncarriers in lumpy form (700 kg lump coal/ton pig iron), supply ducts 11for oxygen-containing gases (275 Nm³ O₂ /ton pig iron) as well asoptionally supply ducts for carbon carriers, such as hydrocarbons, thatare liquid or gaseous at room temperature as well as for burned fluxes.

In the melter gasifier 5, in a lower section I below the meltdowngasifying zone 6, molten pig iron 12 (1000 kg pig iron/ton pig iron) ormolten steel pre-material respectively and molten slag 13 (303 kg/tonpig iron) collect, which are tapped off via a tap 14.

The average analysis of the pig iron is as follows:

C 4.3%

Si 0.4%

Mn 0.08%

P 0.1%

S 0.05%

balance (Fe)

Average slag basicity: B2 (CaO/SiO₂)=1.1

In a section II of the melter gasifier 5 arranged above the lowersection I a bed 16 is formed from the solid carbon carriers, preferablya fixed bed and/or a fluidized bed. The upper section III provided abovethe central section II serves as a killing space for the reducing gasforming in the melter gasifier 5 and for solid particles entrained bythe gas stream formed by the reducing gas.

The pre- or completely reduced fine ore is introduced into the meltdowngasifying zone 6 by means of an oxygen burner 15 directed downward fromabove and oriented approximately vertically, with the burner head 15'being positioned closely above the surface 17 of the bed 16. Withrespect to the cross-section of the melter gasifier 5 the burner head15' is arranged in the central region of the same, i.e. spaced apartfrom the side wall of the same. Preferably only a single burner head 15'is provided, which is positioned on the vertical longitudinal centerline of the melter gasifier 5. The burner 15 is provided with a centralinner pipe 18 for feeding the partially or completely reduced fine oreand with an annular gap 20 for feeding oxygen (275 Nm³ O₂ ton pig iron)or an oxygen-containing gas respectively, which surrounds the centralinner pipe 18 and is delimited by a cooled outer pipe 19.

At the exit site of the oxygen-containing gas and of the suppliediron-containing material a high-temperature combustion zone 21 is formedin which the iron-containing material blown in via the burner head inthe direction of the surface 17 of the bed 16, due to being slowed downon the surface 17 of the bed 16 and by impinging on the said surface 17,reaches a retention time that is sufficient for melting theiron-containing material. The slag thus formed and the molten iron canrun off through the bed 16 to the lower section I of the melter gasifier5.

It may be of advantage, particularly in case of major fluctuations inthe grain size of the charged fine ore or in case a certain portion ismade up of coarser ore particles, to fractionate the iron-containingmaterial emerging from the fluidized bed reactor 1 and to feed only thefine-grain fraction to the burner 15 while charging the coarse-grainfraction (preferably 2 to 8 mm) (530 kg/ton pig iron) via a separatesupply duct 22 and supply openings 23 in the upper section of the meltergasifier 5 into the same. Preferably, the grain size of the particlessupplied via the burner 15 ranges from 0 to 2 mm.

Details concerning the coal:

ultimate analysis:

C 73.6%

H 4.4%

N 1.7%

O 6.2%

S 1.0%

Cfix 60.8%

volatiles 25.6%

ashes 8.6%

grain size of the fine coal:

0 to 2 mm

grain size of the lump coal:

8 to 50 mm

In close vicinity of the burner head 15', lance openings 24 arepositioned of supply lances 25 supplying fine coal (250 kg/ton pigiron). Thus it becomes feasible to blow fine coal into thehigh-temperature combustion zone 21 from the side to a level below theburner head 15', thereby making it possible to prevent oxidation of thepartially or completely reduced fine ore by the oxygen supplied via theburner head 15'.

The supplied fine coal further enables a reduction in the temperature ofthe reducing gas formed in the meltdown gasifying zone 6, which then canbe discharged like in conventional melter gasifiers.

A dust separating means becomes unnecessary for the reducing gas as wellas a dust recircling means, since in the fluidized-bed reduction zone 3of the fluidized-bed reactor 1 the coke dust discharged along with thereducing gas reduces the danger of "sticking", and thus is by no meansdisturbing and via the oxygen burner 15 reaches the meltdown gasifyingzone 6 again. It may be advantageous, however, with a view to adjustingthe temperature of the reducing gas, to purify a portion of the same andsubsequently recircle it.

I claim:
 1. A process for the production of molten pig iron (12) orsteel pre-products from fine-particulate iron-containing material in ameltdown gasifying zone (6) of a melter gasifier (5), in which, in thepresence of carbon-containing material and oxygen-containing gas at thesimultaneous formation of a reducing gas, the iron-containing materialis melted in a bed (16) formed of solid carbon carrier,wherein theiron-containing material is supplied into the melter gasifier (5)centrally, in the immediate vicinity above the bed, by means of anoxygen-burner (15) under the formation of a high-temperature combustionzone (21), and wherein the reducing gas formed in the melter gasifier isintroduced into a fluidized bed of fine iron ore and said iron ore isreduced thereby.
 2. A process according to claim 1, characterized inthat a burning jet formed in the high-temperature combustion zone (21)is directed towards the surface (17) of the bed (16) and is utilized forblowing the iron-containing material towards the surface (17) of the bed(16).
 3. A process according to claim 1, characterized in that fine coalis introduced into the high-temprature combustion zone (21) directly. 4.A process according to claim 1, characterized in that fine ore isreduced in the fluidized bed process (3) by means of the reducing gasformed in the meltdown gasifying zone (6), wherein the reducing gasemerging from the melter gasifier (5) is conveyed to the fluidized bedreduction (3) directly, without prior dust separation.
 5. A processaccording to claim 1, characterized in that lumpy carbon-containingmaterial as well as lumpy iron-containing material are additionallyintroduced into the meltdown gasifying zone (6) via supply ducts (10,22, 23) leading into the upper section of the melter gasifier (5).
 6. Aplant for carrying out the process according to claim 1, comprising amelter gasifier (5) including supply and discharge ducts (4, 7, 10, 11)for adding carbon-containing material, iron-containing material, fordischarging the reducing gas produced and for feeding oxygen-containinggas, as well as a slag and iron-melt tap (14), wherein a lower section(I) of melter gasifier (5) is provided for collecting the molten pigiron (12) and liquid slag (13), a superimposed central section (II) isprovided for accommodating a bed (16) of solid carbon carriers andsubsequently an upper section (III) is provided as a killing space,characterized in that a burner (15) supplying an oxygen-containing gasand fine-particulate iron-containing material into the melter gasifier(5) is provided whose burner head (15') is arranged at the transitionfrom the central section (II) to the upper section (III) in the heart ofthe cross section of the killing space.
 7. A plant according to claim 6,characterized in that the burner head (15') is directed towards thesurface (17) of the bed (16).
 8. A plant according to claim 6,characterized in that lance openings (24) of supply lances (25) feedingfine coal are provided in the immediate vicinity of the burner head(15').
 9. A plant according to claim 6, characterized in that the burner(15) is designed as a burning lance protruding into the interior of themelter gasifier (5) vertically and centrally, departing from the head ofthe melter gasifier (5).
 10. A plant according to claim 8, characterizedin that the supply lances (25) protrude into the melter gasifier (5)departing from the side.
 11. A plant according to claim 6, characterizedin that departing from the killing space (III) of the melter gasifier(5) a reducing-gas discharge duct (7) runs directly, with no dustseparating means arranged intermediately, into a fluidized bed reactor(1) utilized for directly reducing fine-particulate iron ore, and thatdeparting from the fluidized bed reactor (1) a duct (4) for dischargingreduced fine ore runs into the burner (15).
 12. A process according toclaim 1, wherein the particulate iron-containing material is reducedsponge iron.
 13. A process according to claim 1, wherein the particulateiron-containing material is previously completely reduced.
 14. A processaccording to claim 3, wherein the fine coal is blown into thehigh-temperature combustion-zone.
 15. A process according to claim 10,wherein the supply lances slant downwards.